Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$168.54	4.695%	$176.453	$176.45	$176.45	$176.50
Purchase #2	$156.47	10.420%	$172.7742	$172.77	$172.75	$172.80
Purchase #3	$20.64	3.793%	$21.4229	$21.42	$21.40	$21.40
Purchase #4	$219.50	10.844%	$243.3026	$243.30	$243.30	$243.30
Purchase #5	$204.52	3.711%	$212.1097	$212.11	$212.10	$212.10
Purchase #6	$167.50	9.317%	$183.106	$183.11	$183.10	$183.10
Purchase #7	$68.26	6.250%	$72.5263	$72.53	$72.55	$72.50
7 purchase totals =	$1,005.43		$1,081.6947	$1,081.69	$1,081.65	$1,081.70